In recent years, light emitting diode (LED) has been widely applied and plays an increasingly more important role in various fields like display system, lighting system and automobile tail light. The LED with AlGaInP-based light-emitting layer has high internal quantum efficiency. However, external quantum efficiency of conventional LED has been restricted by many factors, like internal total reflection, metal electrode blocking and light absorption by GaAs semiconductor material. For those LEDs growing over light-absorption substrates, a good part of light is finally absorbed by the substrate. Therefore, for those conventional LED structures, external quantum efficiency remains low even internal photoelectric converting efficiency is high. Methods to improve LED light extraction efficiency include thinning window layer, surface roughening, transparent substrate, inverted pyramid structure, etc.